[MikeGale]

Facebook does this already. Not only posts and comments but also messages between two people.

The system is used to hide content, change content, shadow ban and the like.

Even by its own standards it's typically used incorrectly, but most users have no workable way to appeal.

The content reviewed is often visible to low paid workers in various countries. Similar systems have been infiltrated by hostile governments. (Twitter is a case in point.)

(If you use FB you can sometimes probe the system and better establish the details.)

The system is also used to prevent one user informing another that they've been squelched.

My guess, this would give rise to even less competent implementations and actual elimination of political opponents and the like.

[tvink]

"does this" is maybe a little misleading here. Facebook has their own platform which they monitor. Like or not, that's something very different than mandating that every system should have a backdoor.